The present invention relates to a clock signal generator and a method of generating a clock signal.
Many electronic devices utilize clock signals, for example, in synchronisation, time measurement and delay generation. Such clock signals need to be accurate and stable with respect to the supply voltage and temperature. Known clock signal generators commonly use a quartz crystal, but such quartz crystals are relatively bulky and expensive.
It is an aim of the present invention to provide an improved clock signal generator and an improved method of generating a clock signal.
The present invention provides a clock signal generator in an integrated circuit semiconductor device, comprising: a semiconductor substrate; an oscillator unit which comprises at least one support member which is fixed relative to the substrate, an oscillator arm which is oscillatably disposed to the at least one support member with regard a reference position, which oscillator arm includes first and second conductive sections at positions extended from the at least one support member, and at least one biasing or restoring element for biasing or applying a restoring force to the oscillator arm towards the reference position; a driver which is disposed at the substrate in spaced relation adjacent one of the conductive sections of the oscillator arm, which driver is configured in use to drive the one of the conductive sections of the oscillator arm towards or away therefrom when an electrical signal is applied thereto; a sensor which is disposed at the substrate in spaced relation adjacent the other of the conductive sections of the oscillator arm, which sensor is configured in use to generate an electrical signal dependent upon the spacing of the other of the conductive sections of the oscillator arm therefrom; loop circuitry which in use receives the variable electrical signal generated by the sensor and in response thereto applies an electrical signal to the driver so as to cause oscillation of the oscillator arm at the natural oscillating frequency of the oscillator arm; and a clock signal output which is responsive to the variation in the variable electrical signal generated by the sensor so as to provide a clock signal.
Preferably the sensor comprises a transistor which is configured such that the conductivity thereof is dependent upon the position of the other of the conductive sections of the oscillator arm.
Preferably the transistor is a MOS transistor which together with the other of the conductive sections of the oscillator arm defines a resonant double-gate transistor.
Preferably the oscillator arm oscillates by means of the torsional motion of the biasing element.
Preferably the driver comprises a conductive layer, which is disposed above the substrate, and together with the one of the conductive sections of the oscillator arm defines a capacitor.
Preferably the conductive layer is formed of polysilicon.
Preferably the driver comprises a conductive region in the substrate, which together with the one of the conductive sections of the oscillator arm defines a capacitor.
Preferably one or both of the one and the other of the conductive sections of the oscillator arm is formed of polysilicon, doped crystalline silicon or metal.
Preferably the oscillator arm is formed of polysilicon, metal or doped crystalline silicon.
Preferably the oscillator unit is formed as a single integral unit.
Preferably the oscillator arm is a substantially rigid member.
Preferably the oscillator arm is a generally planar member.
Preferably the oscillator arm comprises an elongate member.
Preferably the conductive sections of the oscillator arm are disposed on opposite sides of the at least one support member.
Preferably one of the one and the other of the conductive sections comprises one end of the oscillator arm.
Preferably the other of the one and the other of the conductive sections comprises the other end of the oscillator arm.
Preferably the loop circuitry includes a signal amplifier.
Preferably the loop circuitry includes a signal phase adjuster.
Preferably the clock signal generator, further comprising a further sensor which is disposed in spaced relation adjacent the one of the conductive sections of the oscillator arm, which further sensor is configured in use to generate an electrical signal dependent upon the spacing of the one of the conductive sections of the oscillator arm therefrom, and a differential circuit which in use receives the variable electrical signals generated by the first and further sensors so as to detect differences in those signals and thereby reduce noise.
The present invention also provides a method of generating a clock signal, comprising the steps of: providing an integrated circuit semiconductor device which comprises an oscillator unit which comprises at least one support member which is fixed relative to a semiconductor substrate, an oscillator arm which is oscillatably disposed to the at least one support member with regard a reference position, which oscillator arm includes first and second conductive sections at positions extended from the at least one support member, and at least one biasing element for biasing the oscillator arm towards the reference position, a driver which is configured to drive one of the conductive sections of the oscillator arm towards or away therefrom when an electrical signal is applied thereto, a sensor which is configured in use to generate an electrical signal dependent upon the spacing of the other of the conductive sections of the oscillator arm therefrom; applying a voltage to the driver to move the one of the conductive sections of the oscillator arm relative thereto; sensing movement of the other of the conductive sections of the oscillator arm using the sensor which generates an electrical signal dependent upon the spacing between the other of the conductive sections of the oscillator arm and the sensor; using the variable electrical signal generated by the sensor to alter the voltage applied to the driver so as to cause oscillation of the oscillator arm at the natural oscillating frequency of the oscillator arm; and forming a clock signal dependent upon the variation in the electrical signal generated by the sensor.